style.css

body {
    text-align: center;
    font-family: 'Roboto', sans-serif;
    user-select: none;
}

.titulo {
    font-size: 50px;
    font-weight: bold;
    color: #008080;
}

.quadrados {
    display: flex;
    justify-content: center;
    align-items: center;
}

.quadrado {
    background: #eee;
    font-size: 60px;
    cursor: pointer;
    color: #eee;

    margin: 5px;

    width: 100px;
    height: 100px;
    
    display: flex;
    justify-content: center;
    align-items: center;
}

.jogador {
    margin-top: 30px;
}

.vencedor {
    margin-top: 10px;
}


.jogador, .vencedor {
    font-size: 30px;
    height: 45px;
}

button {
    margin-top: 30px;
    width: 200px;
    height: 30px;
    background: #7fbfbf;
    cursor: pointer;
    font-size: 20px;

    border: 0;
    border-radius: 8px;
    
    transition: all 0.2s;
    transition-property: background-color, color;
}

button:hover {
    background: #329999;
    color: #eee;
}

button:active {
    background: #008080;
}